Current-varying apparatus and terminal member



@ March 1, 1949. MUCHER I 2,463,045

CURRENT-VARYING APPARATUS AND TERMINAL MEMBER Filed Oct. 19, 1945 2 Sheets-Sheet l INVENTOR ATTORNEYS March 1, 1949. G. J. MUCHER 2,463,045

CURRENT-VARYING APPARATUS AND TERMINAL MEMBER Filed Oct. 19, 1945 Ef i 2 Sheets-Sheet 2 INVENTOR fiwfgk I flue/Mr ATTORNEYS Patented Mar. 1, 1949 UNITED STATES PATENT OFFICE CURRENT-VARYING APPARATUS AND TERMINAL MEMBER Application October 19, 1945, Serial No. 623,231

5 Claims.

This invention relates to a structurally and functionally improved current-varyin apparatus as well as a terminal member. In its more specific aspects, the invention aims to provide a structure and member which will be particularly useful in electrical units such as potentiometers and rheostats.

It is well appreciated that considerable difficulty has been experienced in connection with electrical resistances. More particularly, the resistance surfaces or windings have ordinarily had at least one of their ends defined by a raised zone. This has usually come into being as a result of employing a binding strip or clamp which might also provide the terminal. The contact element or end of the contact arm, in traversing the resistance surface, has assumed a position adjacent the end of that surface and subsequent movement in the same direction has resulted in its shifting into the afore-mentioned zone. a consequence of the binding strip defining an elevated plane, the contact has, in effect, been lifted out of electrical engagement with the resistance surface as it has moved into the zone.

It is an object of the present invention to overcome the difficulty afore-enumerated. Conse quently, it will be feasible for the contact arm or element to properly traverse a resistance surface through to its effective end and without moving out of electrical connection with such surface at a point in advance of where the surface terminates. Therefore, a proper traversal of the windings or surface may occur throughout the full range or value of the resistance and even including the end portions or windings thereof.

A further object is that of furnishing a terminal member, the use of which will in no wise encumber or detract from the instrument of which it forms a part and despite the fact that the foregoing advantage obtains by following the teachings of the present invention.

A still further object is that of furnishing a unit of this type which may readily be combined with an instrument and which, when so combined, will provide a unitary structure requiring no further servicing or adjustment.

An additional object is that of designing a terminal member which may embody one of various forms, all of which may be produced by quantity production methods at a relatively nominal figure.

With these and other objects in mind, reference is had to the attached sheets of drawings illustrating practical embodiments of the invention, and in which:

p wire convolutions.

Fig. 1 is a plan view showing somewhat diagrammatically a resistance and a contact arm in association therewith;

Fig. 2 is an edge view of this assembly;

Fig. 3 is an inverted fragmentary perspective View of the end of the resistance element with the end strip or terminal mounted thereon;

Fig. 4 is a fragmentary side view of the end of the resistance element and showing the same in process of traversal by the contact arm.

Fig. 5 is a face view of a unit embodying an alternative form of construction;

Fig. 6 is a sectional side view taken along the lines 66 and in the direction of the arrows as indicated in Fig. 5;

Fig. '7 is an enlarged fragmentary sectional view taken alon the lines (-4 and in the direction of the arrows as indicated in Fig. 5;

Fig. 8 is a further enlarged fragmentary sectional view of a portion of a resistance and showing a contact arm in cooperation therewith;

Fig. 9'is a perspective view of a resistance unit in partially completed form; and

Fig. 10 is a similar view of the type of terminal member which may be applied to the adjacent end of that resistance unit.

In the illustrated embodiment, a certain type of electrical unit has been shown. Likewise, a resistance consisting of a coil has been shown. As will be appreciated from a review of this specification, the invention is applicable for use in connection with various types of electrical instruments. Also, it may be utilized in conjunction with resistances not necessarily involving Therefore, except where otherwise indicated in the claims, the present drawings and description are to be considered in an illustrative rather than a limiting sense.

Thus, as in Fig. l, the reference numeral 30 indicates a resistance element provided by a suitable body formed of di-electric material around which convolutions of wire are wound. This body, as shown, is preferably disposed to have an arcuate or substantially circular configuration. Its edge is traversed by a contact arm 3| or a similar unit which may be supported by a rotor 32 operated by a shaft 33.

For a more detailed showing of the assembly as embodied in a rheostat or potentiometer, reference is had to the illustrations of Figs. 5 and 6 hereinafter more fully described. However, as will be understood with respect to Figs. 1 and 2, the ends of the winding of the resistance 30 are connected to leads (not shown) extending to certain portions of the circuit. To this end will be seen, the terminals which have beenshown as strips 34 are formed with apertures 35 which are aligned with apertures in the main mounting 36. The clip thus furnished may be secured against displacement in any desired manner. As shown in Fig. 3, its ends may be spaced from each other an appreciable distance. Preferably, one end of the clip portion terminates in the form of a tongue 38. This may be extended through the aperture 35 of the mounting. As shown in Fig. 4, it may be bent upon itself to underlie the body of the clip, thus, in efiect, locking the parts against displacement. One clip may be secured adjacent each end of the resistance or any other desired arrangement of the parts may be resorted to.

The contact arm 3| as shown especially in Fig. 4 includes a winding-engaging portion which is slightly curved. Obviously, as the contact arm traverses the windings the electrical values in the circuit will be altered. Adjacent the path of travel of the arm the terminal or strip 34 is notched as indicated at 31.

It is apparent that the zone of the convolutions overlain by the body of the strip is shorted by that body. Therefore, the notch 31 provides, in effect, an indentation through which portions of convolutions having a common electrical value are exposed. Consequently, the contact arm, in moving towards a terminal will traverse convolutions with changes in the electrical values of a circuit occurring. This will continue until the last convolution beyond the zone of the terminal is traversed. As the contact arm traverses convolutions within the zone of the notch, no further changes in electrical value will occur.

In other words, if a given terminal represents, for example, a zero value, the contact arm, in moving towards that terminal, will cause a constantly diminishing electrical flow to occur through certain portions of a connected circuit. This result will obtain right up to the last convolution beyond the terminal zone. Due to the fact that the contact arm is not under the necessity of riding onto the terminal as it reaches what might be termed the zero zone, it follows that 'it is' not elevated or lifted out of contact with the convolutions. Rather, any lifting which may "occur will only result after it has entered that zone. Therefore, even if this action occurs it will not be electrically noticeable.

An alternative form of construction, whereby the same results may be achieved is illustrated in the structures shown in Figs. 5 to 10. In these jviews, the reference numeral Ill indicates a shell and a terminal l9 may be suitably connected with the rotor to furnish a' current path to the arm 'or contact l3 thereof.

The foregoing is again merely illustrative of a generally acceptable type of layout. As will well be understood, the resistance might take a form quite different from that herein illustrated. The same is true of the contact or arm I3 as well as the mechanism for mounting and shifting the same. Additionally, two terminals I1 and [8 will not have to be employed in certain types of units. The foregoing description, taken in connection with Figs. 5 to 10 of the drawings is, however, illustrative of a second typical form of unit in which the present invention may be embodied.

In lieu of the strip or band defining the end zone of the resistance as in Figs. 1 to 4, a member such as has been illustrated in Fig. 10 may be employed. In that view, it will be seen that the terminal I! is continued in the form of a body 20 terminating in an inwardly and downwardly extending portion 2!. This body is of an area such that it may be applied to or constricted around the body 12 and the resistance mounted thereby. Thus, if it is applied to the body adjacent the end of the latter, this member will define the end zone of the resistance. Preferably, and as shown in Fig. '7, a notch 22 may be provided as part of the assembly and in order to define a recess such that the terminal member may be received therein and thus properly disposed with respect to the winding.

In line with the zone or path of travel of the contact arm or element l3, the body 20 presents in cross section a wedge or knife structure. This has been indicated at 23. Beyond the reduced edge of this structure, the increase in depth over and beyond the space defined by the windings or other resistance surface is negligible. Therefore, the contact arm or element l3 may traverse the resistance surface and begin to shift onto the body 20 without the circuit being broken between the arm l3 and the surface of the resistance. Therefore, it is apparent that the arm may provide for variation in the current fiow down to and including the last winding or end zone portion of the resistance and despite the fact that the contact is riding into a position overlying the body 20. This has been especially shown in Fig. 8.

Consequently, it is feasible to combine a unit including a terminal member constructed in accordance with the present teachings into a layout of apparatus with assurance that the unit may be operated effectively throughout its entire range. Therefore, delicate and critical apparatus to which the unit is connected may also be caused to respond throughout the entire range of the resistance. At the same time, it will be understood that the use of the terminal member constructed in accordance with the present teachings will in no wise encumber the unit to which it is applied nor impair the operation of the latter.

Thus, among others, the several objects of the invention as specifically afore-noted are achieved. Obviously, numerous changes in construction and rearrangements of the parts might be resorted to without departing from the spirit of the invention as defined by the claims.

I claim:

1. A terminal member for application to a resistance to be traversed by a contact, said member comprising a body having an area tapered in cross section to define a reduced leading edge providing a trackway for said contact.

2. A terminal member for application to a resistance, said member comprising an encircling body portion, and having a portion of one of its edges reduced in thickness to define a tapered trackway area onto which a contact may pass.

3. A terminal for application to a resistance, said terminal embracing a body comprising a strip of material bent to provide parts lying in face to face contact with the opposite sides of a resistance strip, end portions connecting said parts and to lie adjacent and extend around opposite edges of said resistance strip, said material strip being formed with an opening to be aligned with an opening formed in a resistance to which it is to be applied and one of said end portions being extendable through said opening.

4. An apparatus of the character described, including in combination a mounting member formed with an aperture, windings of resistance wire encircling said member, a metallic terminal strip formed with an aperture aligned with the aperture of said member, the body of said strip being disposed in contact with, and overlying the winding of one face of said member, the ends of said strip being bent to extend around the edges of the mounting member and engaging the face of the same opposite to that engaged by said strip body and a tongue extending from one of said ends and passing through the apertures of both said strip and member.

6 5. An apparatus of the character described, in-

cluding in combination a mounting member formed with an aperture, windings of resistance wire encircling said member, a metallic terminal strip formed with an aperture aligned with the aperture of said member, the body of said strip being disposed in contact with, and overlying the winding of one face of said member, the ends of said strip being bent to extend around the edges of the mounting member and engaging the face of the same opposite to that engaged by said strip body, one of said ends having a width less than that of the strip body and a tongue defining the outer portion of said end, said tongue extending through both the apertures of said strip and member.

GEORGE J. MUCHER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,913,686 Schellenger June 13, 1933 1,917,675 Weichelt July 11, 1933 2,005,456 Creager June 18, 1935 

